do you know any soft for calcurating area of picture

do you know any soft for calcurating specified area of PICT or other
format of picture,I intend to use this for calcurating area such as
nucleus or tumor cells. If you do let me know by Email. my address is
tkiji at med.nihon-u.ac.jp(the soft should have automatic area selecting
device by colour like the one in photoshop) thank you